That’s a harp guitar, folks, being played by Andy McKee [via LGF. Charles Johnson erroneously describes it as “mutant harp/guitar.”] This is the same Larson-Dyer version that I learned on; it was my great grandfather’s, and I still have it. It’s got a wide fretboard with 6 strings and 6 free bass strings above (hence the “harp” moniker). I’d never heard one played properly until I saw this video.